1. Technical Field
The present invention relates generally to liquid level controllers, and more particularly to an automatic liquid level control system having a remote sensor for sensing the liquid level in a container, wherein the sensor is in communication with an electronically activated control valve that regulates the fill level in the liquid container.
2. Background Art
Maintaining a constant volume of liquid in a container is important in several industrial and non-industrial arenas. Liquid level variations are particularly problematic when a large surface area of the liquid is exposed to the atmosphere, resulting in large liquid losses due evaporation. This is especially problematic in swimming pools, which also suffer large water volume losses due to splashing.
The reliable control of water level in a swimming pool is imperative for a number of reasons: firstly, pool filters can malfunction if the water level falls too low; secondly, damage to pool surfaces and sidewalls may result from exposure due to low water; thirdly, the chemical balance of swimming pool water depends on tight control of the chemical composition, and this balance is undermined by the addition or removal of large volumes of water, resulting in decreased microbicidal effectiveness and/or discomfort to swimmers due to high chemical concentrations. Thus, automatic control over swimming pool water level is desirable inasmuch as it helps to address these concerns without constant monitoring and intervention.
It is also desirable to provide for the automatic control of swimming pool water level in order to reduce the time and labor involved in correcting deviations from the optimum level. As a practical matter, deviations from an optimum water level may not be noticed until the deviation is quite large, and filing or draining a large volume of water may take several hours in a sizable pool. Accordingly, it is preferable to have a system that constantly monitors and detects small deviations from the optimum water level and regularly makes minor adjustments and corrections as needed.
Several inventions in the prior art employ a float to close an electrical switch and sound an alarm when the float is buoyed to a pre-determined height by water rising in a vessel. The switch is in series with an electrical power source and an alarm, such as a bell or a light, and emits an alarm output signal when the liquid in the vessel reaches a predetermined level. Examples include U.S. Pat. No. 741,759 to Bishop, and U.S. Pat. No. 3,633,193, to Milo. A device deserving notice is disclosed in U.S. Pat. No. 4,771,272 to Barnes, which teaches a liquid level electrical alarm apparatus that comprises a perforated hollow cylindrical sensor housing having upper and lower cup-shaped caps. The housing is suspended from the upper rim of a liquid container by a cable connected to an audible alarm. A cylindrical float contained within the sensor housing contains a permanent magnet near its upper end that closes contact bars of a reed switch element mounted in the upper cap when the float rises a pre-determined level. The sensor body is suspended by a flexible electrical cable connected to the upper cap. Means are provided for adjusting the length of cable from, which the sensor is suspended into a vessel, thereby permitting adjustment of the liquid level which trips the alarm. By means of an alarm, the disclosed devices alert an attendant that a liquid level has arisen to a predetermined level, but they do not provide means for automatically turning on or shutting off a control valve after detecting the level. Thus, manual intervention to correct liquid level disturbances is still required with these devices.
The prior art also includes several systems for automatically controlling the water level of a swimming pool. For example, U.S. Pat. No. 5,878,447 to Mogab et al., discloses an automatic water regulator for automatically filling a swimming pool when the water is below a predetermined level. The water regulator apparatus can be added to any existing built in swimming pool equipped with a skimmer and a water fill line. The water regulator apparatus automatically senses the water level of the swimming pool by attachment to a skimmer lid, establishes if the level is within the allowable range, causes the pool water fill line to turn on if below the allowable range, and subsequently shuts off when the desired water level has been reached. The water regulator apparatus comprises a transmitter assembly and a receiver assembly, which must be fit within a skimmer lid only. The transmitter assembly includes a water level detector that periodically automatically monitors the water level within the pool. If the water level is below a specified threshold, the transmitter assembly sends a radio transmission to be received by the receiver assembly. When the receiver assembly receives the radio transmission, it causes a water fill valve to automatically turn on a water supply to the pool, thereby filling the swimming pool. As the swimming pool is filling, the immersed metal water level detector monitors the water level until the water level has reached the upper immersed metal detector. Once the upper detector has been reached, the transmitter assembly sends a radio transmission to be received by the receiving assembly. When the receiving assembly receives the radio transmission, it causes the water fill valve to automatically turn off the water supply to the pool. This device has application to swimming pools only inasmuch as it is physically configured for attachment to skimmer lid; thus, it is not suited for uses in liquid containers other than swimming pools, as is the present invention.
U.S. Pat. No. 4,380,091 to Lively, discloses circuitry for automatically controlling the water level of swimming pools with a multi-level detecting sensor for directly sensing the pool water. A low voltage oscillator in the input portion of the circuitry detects the presence of water above or below each level sensing electrical contact of the sensor by a change in oscillator amplitude in response to impedance from the contact to ground. Signal threshold circuitry changes in output signal in response to the amplitude of the oscillator signal. Delay circuitry integrates the output of the threshold signal to avoid responding to spurious changes in water level, such as wave action in the pool. Monitor circuitry disposed between the delay circuitry and the water fill, water dump, and pump control circuitry monitors signals received from the sensor or generated by the input circuitry to detect any malfunctions in the sensor or the control circuitry, such as improper sequence of the water level signals, to disable further filling of the pool. Bi-stable switch circuitry controls filling of the pool and is responsive to differing pool levels to cause filling of the pool to commence or to stop.
It is evident that the art is evolving in providing sensing mechanisms having a moveable float and related electronic circuitry in communication with a control valve. However, no device or devices known to date provide a liquid level controller having a receiver in communication with a remote, fully enclosed plastic sensor having (1) programmable logic means for distinguishing anomalous and/or transitory liquid level fluctuations from level changes requiring correction through the opening of a liquid supply control valve, (2) a fail safe shutoff system, and (3) a housing and functional electronics each adapted for installation in any fluid container.